Spark plug shielding

ABSTRACT

Shielding for spark plugs of internal combustion engines to prevent radio frequency interference and explosion, the shielding having a body surrounding the spark plug and engaged with the wrench portion of the spark plug and having a wrench portion to enable installation and removal of the spark plug, the body having at one end a threaded end piece securing the plug in place and being threaded at the other end to accommodate a spark plug connector terminal. Internally, the spark plug is encircled by an insulating sleeve, and a seal is provided to prevent entry of explosive gas into the body.

United States Patent [151 3,697,796 Livingston 1 Oct. 10, 1972 [54] SPARK PLUG SHIELDING 2,458,121 1/1949 Waldron ..3l3/ 134 X [72] Inventor: Russell G. Livingston, 6044 Rod Avenue, Woodland Hills, Calif. l 9 a 91364 Assistant Examiner-Siegfried H. Grimm Attorney-Newton H. Lee, Jr. [22] Filed: July 27, 1970 211 App]. No.1 58,592 [57] ABSTRACT Shielding for spark plugs of internal combustion engines to prevent radio frequency interference and ex- [52] 313/134 gh gfi plosion, the shielding having a body surrounding the [51] Int Cl 13/06 spark plug and engaged with the wrench portion of the 581 Field 6r sa ;c ll. i/ i 3 i 1 3 5 1 3 7 123/148 P Spark P and havmg a wrench enable 123/169 i stallation and removal of the spark plug, the body having at one end a threaded end piece securing the plug in place and being threaded at the other end to ac- [56] References cued commodate a spark plug connector terminal. lnter- UNITED STATES PATENTS nally, the spark plug is encircled by an insulating 2 303 389 12/1942 R b 22 3 3/ 3 x sleeve, and a seal 15 provided to prevent entry of exaeana l 2,399,390 4/1946 Robertson ..313/134 x p g n O e y 2,177,268 10/1939 Stone et a1. ..313/134 X 8 Claims, 3 Drawing Figures SPARK PLUG SHIELDING BACKGROUND OF THE INVENTION The operation of internal combustion engines using a spark ignition system results in the production of radio frequency interference signals emanating from the ignition system. As a consequence, various shielding devices have heretofore been provided for use about the spark plugs of the ignition system, as well as in combination with the ignition wiring harness and other components to prevent radio interference. In addition, arcing of spark plugs and in other portions of an ignition system for internal combustion engines poses a further problem when the engine is operating in a potentially explosive enviroment, say at an oil or gas well drilling or production site where explosive gas may be present, as well as in other installations, such as in boats, where explosive gas may accumulate and where a spark may initiate an explosion.

While a spark plug may be encased in a permanent shield to obviate these problems, the permanent shielding is economically undesirable, since the spark plug is often replaced, with the result that the shielding is also replaced. Moreover, the usual removable radio frequency interference shielding devices for spark plugs heretofore available have not provided effective protection against explosion.

SUMMARY OF THE INVENTION The present invention provides a removable spark plug shielding device which is effective as a radio frequency interference shield and also as a shield against arcing in an explosive environment.

More particularly, the invention provides a shield which is associated with the spark plug in such a manner that the shield also functions to enable installation and removal of the spark plug, in that the shield has internal surfaces which engage the usual wrenching section of the spark plug, and the shield also has external wrenching surfaces by which the shield and the spark plug are adapted to be rotated.

In order for the shield to be explosion proof, the invention also contemplates the provision of sealing means in the assembly to prevent the admission of explosive gas into the shield. Such sealing means may be constituted by an internal insulator which is forced into sealing engagement with the spark plug and with the shoulder of the shield, or the sealing means may be a separate sealing ring engageable with the spark plug. The admission of explosive gas into the shield at the outer end of the spark plug is prevented by a seal incorporated in the connector which connects the spark plug wire to the spark plugs.

An object of the invention is to provide a spark plug shield, as generally described above, which is simple of manufacture to fit all of the standard spark plugs, which is inexpensive to use, since it enables repeated use with different spark plugs, and which is easy to assemble with the spark plugs.

This invention possesses many other advantages, and has other purposes which may be made more clearly apparent from a consideration of forms in which it may be embodied. These forms are shown in the drawings accompanying and forming part of the present specification. They will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed descriptions are not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a spark plug shield assembly embodying the invention;

FIG. 2 is a longitudinal section through the assembly of FIG. 1, but with the spark plug shown in elevation; and

FIG. 3 is a fragmentary longitudinal section of a modified form of seal for the shield.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As seen in the drawings, the invention comprises a shield assembly S adapted to be applied to a spark plug P and adapted to have a spark plug wire W connected to the shield and electrically connected to the spark plug by a connector C.

The spark plug P is a typical one, including a threaded base 10 adapted to be threaded into a cylinder head so that an are at the gap 11 will ignite the fuel charge in the cylinder. The plug P also includes a porcelain insulator 12 which surrounds the usual conductor to insulate the latter from the body 13 of the plug. Included on the body 13 of the plug is a wrenching section 14 which is characteristically hexagonal in form; whereby the plug is adapted to be threaded into or removed from the engine. At the outer end of the plug P, is the usual connector post 15 which is adapted to be electrically connected to the spark wire W by the connector C.

More particularly, the shield S comprises an elongated hollow body 16 which is formed at one end, as at 17, to provide an internal socket configuration complemental to the external configuration of the wrenching section 14 of the plug P, whereby the body 16 is adapted to rotate the plug P into or from the threaded socket of an engine block. Externally, the body 16 is threaded at 18 to receive a nut 19 having a flange 20 engageable with the under-surface 21 of the wrenching section 14 of the plug to tightly hold the wrenching section 14 in the socket 17. The shield also includes an adaptor section 22 providing a wrenching section 23, preferably, for convenience, of the same hexagonal configuration and size as the wrenching section 14, so that the same spark plug wrench that fits the spark plug will also fit the adaptor. At its outer end, the adaptor 22 is threaded at 24 to receive the connector C. Preferably, the body 16 and the adaptor 22 are separate elements, facilitating the production of the body 16 by an upsetting operation to form the socket 17. Under these circumstances, the adaptor has a cylindrical end portion 25 which is fixed in the outer end of the body 16 as brazing, or the like, whereby substantial torque may be transmitted from the adaptor 22 to the body 16. In addition, this connection is gas tight. The adaptor 22 may be conveniently turned from hexagonal bar stock, and drilled to provide the bore 26 therein. The materials of the body 16 and adaptor 22 are preferably steel so as to enclose the spark plug P and its connection with the connector C in an effective shield against the radio frequency energy radiated from the plug when it is energized.

Referring particularly to FIG. 2, it will be seen that the sleeve 27 of suitable insulating material which surrounds the porcelain 12 of the plug and the connection with the connector C, whereby no arcing may occur between the plug P and the shield S. In this embodiment, the insulating sleeve 27 is preferably composed of resilient material, such as a molded fluoro-carbon, whereby the resiliency may be availed of to provide sealing means for preventing the entry of explosive gas into the shield in the region of the electrical connection between the spark plug P and the connector C. In accomplishing this seal, the outer end of the sleeve 27 abutts an annular shoulder 28 provided in the adaptor 22, and the inner end of the sleeve 27 abutts an annular shoulder 29 on the spark plug P. If the sleeve 27 is at least slightly longer than the distance between the shoulders 28 and 29 when the spark plug and shield are assembled together, the ends of the sleeve 27 will be maintained inpressure contact with the shoulders 28 and 29. The seal at the shoulder 28 prevents the passage of gas into the sleeve 27 from the annular space between the sleeve and the shield body 16 and adaptor 22, and the seal at the spark plug shoulder 29 prevents the passage of gas into the sleeve 27 between the plug and the sleeve.

Other sealing means may be employed, as, for example, shown in FIG. 3, wherein a resilient washer 30 is placed in the socket 17, and forms a seal between the plug section 14 and the inner wall of the socket 17 to prevent passage of gas along the annular space between the sleeve 27 and the shield body 16 and adaptor 22, as well as a seal between the lower end of the sleeve 27 and the shoulder 29 on the plug, to prevent passage of gas into the sleeve 27 between the sleeve and the plug.

The connector C, now to be described, is constructed in such a manner that the union between the connector and the adaptor 22 is sealed to preclude entry of gas into the region of the electrical connection, so that the shield is fully explosion proof.

More particularly, the connector C comprise a fitting 31 having an opening 32 for the ignition or spark plug wire W. Externally, the fitting 31 has a flange 33 for engagement with a connector nut 34 which is adapted to be applied to the outer end of the adaptor 22 on the threaded section 24 of the latter. Within the nut, and carried by the wire W is a resilient insulating sleeve 35 having an upper sealing flange 36 which seats against the inner end of the fitting 31 and which also engages the upper end surface of the adaptor 22, whereby when the nut 34 is tightened, the flange is deformed into tight sealing engagement with the contacting surfaces of the fitting and the adaptor, as well as with the wire W. Thus, explosive gas cannot enter the assembly through the connector C.

In order the make contact between the wire W and the post of the spark plug, the end of the conductor 37 is bared, and a coiled contact spring 38 is secured to the conductor 37 by a ferrule 39 which is retained on the conductor by a flare 40 and an expander nail 41.

From the foregoing, it will be apparent that the invention provides a shield for spark plugs which is adapted to render the plug explosion proof and which is also adapted to shield against radio frequency interference. The shield is easily applied to the spark plug and provides its own wrenching section, whereby to install theplug in and remove the plug from an engine without need for special tools.

I claim:

1. A spark plug shield comprising: an elongated hollow body, said body having a socket portion at one end having an inside configuration complemental to the wrenching section of a spark plug and an external thread, said body also having a wrenching section thereon, and insulating sleeve in said body for receiving the porcelain and post of the spark plug, an internally threaded nut threadable on said threads of said socket portion and having an end flange engageable with the wrenching section of said spark plug to hold the latter in said socket, and means at the other end of the body for connection to a spark plug wire connector.

2. A spark plug shield as defined in claim 1, wherein said wrenching section of said body is the same size as the wrenching section of the spark plug which fits said socket.

3. A spark plug shield as defined in claim 1, including sealing means engageable in said body and with said spark plug to prevent the admission of gas into said body through said one end.

4. A spark plug shield as defined in claim 3, wherein said sealing means comprises end portions of said insulating sleeve, one of said end portions being engageable with said spark plug wrenching section, and said body having a sealing shoulder engaged by the other end portion of said sleeve when said nut is tightened on said body to hold the wrenching section of said spark plug in said socket.

5. A spark plug shield as defined in claim 3, wherein said sealing means includes a resilient washer in the bottom of said socket and engageable with the wall of said socket and with said wrenching section of said spark plug when said nut is tightened on said body to hold the wrenching section of said spark plug in said socket.

6. A spark plug shield as defined in claim 3, and including sealed connector means for connecting said spark plug wire to said body and preventing the entry of gas into said body through said connector means.

7. A spark plug shield as defined in claim 1, wherein said body comprises a body section and an adaptor section, means connecting an end of said body section to said adaptor section, said body section having said socket in the other end, and said adaptor having said wrenching section thereon, said adaptor section also having thereon said means for connection to a spark plug wire connector.

8. A spark plug shield as defined in claim 7, wherein said means connecting an end of said body section to said adaptor section comprises a gas tight joint, and including sealing means engageable in said body and with said spark plug to prevent the admission of gas into said body through said socket. 

1. A spark plug shield comprising: an elongated hollow body, said body having a socket portion at one end having an inside configuration complemental to the wrenching section of a spark plug and an external thread, said body also having a wrenching section thereon, and insulating sleeve in said body for receiving the porcelain and post of the spark plug, an internally threaded nut threadable on said threads of said socket portion and having an end flange engageable with the wrenching section of said spark plug to hold the latter in said socket, and means at the other end of the body for connection to a spark plug wire connector.
 2. A spark plug shield as defined in claim 1, wherein said wrenching section of said body is the same size as the wrenching section of the spark plug which fits said socket.
 3. A spark plug shield as defined in claim 1, including sealing means engageable in said body and with said sPark plug to prevent the admission of gas into said body through said one end.
 4. A spark plug shield as defined in claim 3, wherein said sealing means comprises end portions of said insulating sleeve, one of said end portions being engageable with said spark plug wrenching section, and said body having a sealing shoulder engaged by the other end portion of said sleeve when said nut is tightened on said body to hold the wrenching section of said spark plug in said socket.
 5. A spark plug shield as defined in claim 3, wherein said sealing means includes a resilient washer in the bottom of said socket and engageable with the wall of said socket and with said wrenching section of said spark plug when said nut is tightened on said body to hold the wrenching section of said spark plug in said socket.
 6. A spark plug shield as defined in claim 3, and including sealed connector means for connecting said spark plug wire to said body and preventing the entry of gas into said body through said connector means.
 7. A spark plug shield as defined in claim 1, wherein said body comprises a body section and an adaptor section, means connecting an end of said body section to said adaptor section, said body section having said socket in the other end, and said adaptor having said wrenching section thereon, said adaptor section also having thereon said means for connection to a spark plug wire connector.
 8. A spark plug shield as defined in claim 7, wherein said means connecting an end of said body section to said adaptor section comprises a gas tight joint, and including sealing means engageable in said body and with said spark plug to prevent the admission of gas into said body through said socket. 